This invention relates to a process for preparing iminodiacetonitrile by the reaction of formaldehyde, hydrogen cyanide and an ammonia source.
The compound iminodiacetonitrile is a valuable chemical intermediate which is used to prepare iminodiacetic acid or its alkali metal salt, which is also a valuable chemical intermediate that is commercially available and useful for the preparation of a number of chemical compounds, such as the preparation of herbicides, pesticides, chelating agents, and detergent builders.
The prior art discloses a number of processes for the preparation of iminodiacetonitrile. For example, U.S. Pat. No. 3,904,668, to Gaudette et al, discloses that iminodiacetonitrile can be prepared by forming an aqueous mixture of hexamethylenetetramine, HCN, and glycolonitrile, and passing the mixture through a tubular reactor at about 100.degree.-200.degree. C. to form iminodiacetonitrile.
The prior art process that is most generally used for the preparation of iminodiacetonitrile has been that described by U.S. Pat. No. 2,794,044 to Miller, who stated that the obvious equation for the reaction producing iminodiacetonitrile is to react stoichiometric quantities of ammonia, formaldehyde and HCN. When, however, the reactants are mixed in the stoichiometric ratio demanded by the equation, no product can be isolated, regardless of the pH adjustment.
Despite these teachings in the prior art, it has now been found that iminodiacetonitrile can be produced in high yield under modest reaction conditions, contrary to the teachings of the prior art.